Does your poop float or sink? If you have sinkers, it is likely that your colon is congested, even if you are regular.
When one eats enough soluble and insoluble fiber from fresh fruits & veggies not supplements, limits animal-based foods and drink enough water, there is a big difference in the poop. Not only does it float, is softly formed and exits easily, without soiling the anal area.
At that point, you might not need to cleanse the bowels before the flush, though after the flush, you'll want to cleanse the bowel to get rid of the traces of the toxins you removed from the liver.